From e94e761305fa2281718adcf625d78f3cf662e12d Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Thu, 1 Aug 2024 18:12:50 +0100
Subject: [PATCH 1206/1215] dtoverlays: Add overlay for HD44780 via I2C PCF8574
 backpack

Many HD44780 LCD displays are connected via very common I2C
GPIO expander.
We have an overlay for connecting the displays directly to GPIOs,
but not one for it connected via a backpack. Add such an overlay.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
 arch/arm/boot/dts/overlays/Makefile           |  1 +
 arch/arm/boot/dts/overlays/README             | 27 +++++++++
 .../dts/overlays/hd44780-i2c-lcd-overlay.dts  | 57 +++++++++++++++++++
 3 files changed, 85 insertions(+)
 create mode 100644 arch/arm/boot/dts/overlays/hd44780-i2c-lcd-overlay.dts

--- a/arch/arm/boot/dts/overlays/Makefile
+++ b/arch/arm/boot/dts/overlays/Makefile
@@ -82,6 +82,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	gpio-no-irq.dtbo \
 	gpio-poweroff.dtbo \
 	gpio-shutdown.dtbo \
+	hd44780-i2c-lcd.dtbo \
 	hd44780-lcd.dtbo \
 	hdmi-backlight-hwhack-gpio.dtbo \
 	hifiberry-amp.dtbo \
--- a/arch/arm/boot/dts/overlays/README
+++ b/arch/arm/boot/dts/overlays/README
@@ -1705,6 +1705,33 @@ Params: gpio_pin                GPIO pin
                                 (default 100)
 
 
+Name:   hd44780-i2c-lcd
+Info:   Configures an HD44780 compatible LCD display connected via a PCF8574 as
+        is often found as a backpack interface for these displays.
+Load:   dtoverlay=hd44780-i2c-lcd,<param>=<val>
+Params: addr                    I2C address of PCF8574
+        pin_d4                  GPIO pin for data pin D4 (default 4)
+
+        pin_d5                  GPIO pin for data pin D5 (default 5)
+
+        pin_d6                  GPIO pin for data pin D6 (default 6)
+
+        pin_d7                  GPIO pin for data pin D7 (default 7)
+
+        pin_en                  GPIO pin for "Enable" (default 2)
+
+        pin_rs                  GPIO pin for "Register Select" (default 0)
+
+        pin_rw                  GPIO pin for R/W select (default 1)
+
+        pin_bl                  GPIO pin for enabling/disabling the display
+                                backlight. (default 3)
+
+        display_height          Height of the display in characters (default 2)
+
+        display_width           Width of the display in characters (default 16)
+
+
 Name:   hd44780-lcd
 Info:   Configures an HD44780 compatible LCD display. Uses 4 gpio pins for
         data, 2 gpio pins for enable and register select and 1 optional pin
--- /dev/null
+++ b/arch/arm/boot/dts/overlays/hd44780-i2c-lcd-overlay.dts
@@ -0,0 +1,57 @@
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2835";
+
+	fragment@0 {
+		target = <&i2c_arm>;
+		__overlay__ {
+			status = "okay";
+
+			pcf857x: pcf857x@27 {
+				compatible = "nxp,pcf8574";
+				reg = <0x27>;
+				gpio-controller;
+				#gpio-cells = <2>;
+				status = "okay";
+			};
+		};
+	};
+
+	fragment@1 {
+		target-path = "/";
+		__overlay__ {
+			lcd_screen: auxdisplay {
+				compatible = "hit,hd44780";
+
+				data-gpios = <&pcf857x 4 0>,
+					     <&pcf857x 5 0>,
+					     <&pcf857x 6 0>,
+					     <&pcf857x 7 0>;
+				enable-gpios = <&pcf857x 2 0>;
+				rs-gpios = <&pcf857x 0 0>;
+				rw-gpios = <&pcf857x 1 0>;
+				backlight-gpios = <&pcf857x 3 0>;
+
+				display-width-chars = <16>;
+				display-height-chars = <2>;
+			};
+		};
+	};
+
+	__overrides__ {
+		pin_d4 = <&lcd_screen>,"data-gpios:4";
+		pin_d5 = <&lcd_screen>,"data-gpios:16";
+		pin_d6 = <&lcd_screen>,"data-gpios:28";
+		pin_d7 = <&lcd_screen>,"data-gpios:40";
+		pin_en = <&lcd_screen>,"enable-gpios:4";
+		pin_rs = <&lcd_screen>,"rs-gpios:4";
+		pin_rw = <&lcd_screen>,"rw-gpios:4";
+		pin_bl = <&lcd_screen>,"backlight-gpios:4";
+		display_height = <&lcd_screen>,"display-height-chars:0";
+		display_width = <&lcd_screen>,"display-width-chars:0";
+		addr = <&pcf857x>,"reg:0";
+	};
+
+};